(i) Field of the Invention
This invention relates generally to activated preparation of metal alkoxides from metals and alcohols. More particularly, it concerns preparing alkoxides from certain metals and certain alcohols which are not very reactive absent an activator. Typical metals are those from groups 2A, 2B, 3A and 3B. Typical alcohols are those which contain up to 16 carbon atoms. The activators include both catalysts and noncatalysts. Even more particularly, it relates to ball milling the activator and the metal prior to the addition of the alcohol.
(ii) Description of the Prior Art
The use of activators in preparing metal alkoxides from metals and alcohols has been known for decades. Accordingly, summaries of the prior art are available in handbooks. For example, Kirk-Othmer's "Chemical Encyclopedia", Third Edition, summarizes such preparation in the following manner (for a monovalent metal).
"From Metals and Alcohol: Alkali, alkaline earth metals, and aluminum react with alcohols to give metal alkoxides (2-3,61): EQU M+ROH.fwdarw.MOR+1/2H.sub.2
The speed of the reaction depends both on the metal and on the alcohol, increasing with increasing electropositivity and decreasing with length and branching of the chain. Thus sodium reacts strongly with ethanol, but slowly with tertiary butanol. The reaction with alkali metals is sometimes carried out in ether, benzene, or xylene. Some processes use the metal amalgam or hydride instead of the free metal. Alkaline earth metals and aluminum are almost always covered with an oxide film. Slight etching with iodine or mercuric chloride breaks the film and facilitates the reaction".
Aforementioned Kirk-Othmer also discusses their preparation by alcoholysis and transesterification and points out the following: "Metal alkoxides of higher, unsaturated, or branched alcohols are difficult to prepare directly and are usually made from lower metal alkoxides by means of alcoholysis: EQU M(OR)n+nR'OH.revreaction.M(OR')n+n ROH"
An even more comprehensive recent survey is found in "Metal Alkoxides" by D. C. Bradley, R. C. Mehrotra and D. P. Gaur, published by the Academic Press in 1978. "Reactions of Metals with Alcohols" is discussed at pages 10-13 and it is stated that a catalyst "appears to be essential" for "the less electropositive elements such as magnesium, beryllium and aluminum"; and perhaps for yttrium and scandium. It further states that the role of the catalyst in such reactions is not fully understood, but it might involve merely cleaning the metal surface or perhaps the formation of intermediate derivatives which could react more readily with alcohols.
Significantly, neither of the foregoing surveys discloses or suggests that there could be any advantage from grinding an activator and a metal prior to addition of the alcohol.
A computer search of Chemical Abstracts from 1967 to present, concerning the preparation of metal alkoxides, did not turn up any reference which, from its abstract, clearly related to the grinding of a metal. Also, it turned up only one reference which, from it's abstract, clearly related to the use of a catalyst in preparing a metal alkoxide from metal and alcohol. This reference is U.S. Pat. No. 3,717,666 (Kobetz et al.), discussed below.
Aforementioned Kobetz discloses that the reaction of aluminum and alcohol is improved by catalysis with an alkoxy alcohol. The reference states that an important advantage of the Kobetz invention is that it does not require "activation by alloying or mixing with mercury or its compounds, halogens, titanium, silicon, zirconium, sodium, etc. or the need for physical manipulations such as cutting, grinding, powdering or abrading to exceedingly fine particle sizes". The same reference refers to U.S. Pat. Nos. 2,125,961; 2,229,528; 2,579,251; 2,636,865; and 2,666,076.
Aforementioned U.S. Pat. No. 2,636,865 (Kimberlin) relates to preparing aluminum alkoxides by a process wherein there is not even pre-mixing of the catalytic material and the aluminum prior to the addition of the alcohol (for example, see the description in Col. 4, from line 50 to line 68).
Aforementioned U.S. Pat. No. 2,666,076 (Rex et al.) relates to a process for making aluminum alkoxide from aluminum and amyl alcohol or the like. Rex's invention relates to a continuous process wherein large pieces of aluminum are treated with an activating solution (such as a 1% solution of mercuric chloride in amyl alcohol) thereby removing an oxide film from the metal surface; separating the activated aluminum from at least most of the activating solution; and reacting the activated aluminum with an alcohol such as amyl alcohol at elevated temperature. Rex points out that the prior art (as of 1952) "operated largely on the belief that the activation of the aluminum was essentially a catalytic effect, and consequently activating solutions have heretofore generally been added to the main reaction mixture, thereby leading to undesirable contamination". Rex includes a number of negative teachings relative to the invention claimed hereinafter.
U.S. Pat. No. 2,845,447 (Carlson) was cited against aforementioned Kobetz. Carlson appears to relate to an autocatalytic process which "can proceed without added catalyst due to the aluminum in the upper part of the bed being conditioned by the presence of the liquid in the reaction zone in the lower part of the bed" (see claim 1 and col. 6, lines 52-75).
The preparation of yttrium alkoxides is discussed in the "The Preparation and Some Properties of Yttrium, Disprosium, and Ytterbium Alkoxides" by K. S. Mazdiyasni, C. T. Lynch, and J. S. Smith in "Inorganic Chemistry", Vol. 5, No. 3, March, 1966 at pages 342-346. Working examples for yttrium are provided at pages 343-344, for both aliphatic and aromatic compounds; as well as synthesis of heavier alkoxides by substitution of other R groups for the isopropoxy group in an alcoholysis reaction. Yields ranged from 47% to 85%. Interestingly the reference teaches that the reaction can be carried out "in excess alcohol but not in excess mercuric chloride" because of the side reaction in which the alcohol reacts to form an alkene and to produce an alkene oxide as the finished product (see discussion at pages 344-345). The foregoing would appear to be a strong negative teaching against any process involving dry ball milling of mercuric chloride with fine particles of heavily indented and serrated metal, and perhaps forming local high concentrations of mercuric chloride in the crevices.
A second computer search of Chemical Abstracts from 1967 to present was made. This search concerned ball milling of metal as the broadest category. This turned up two references of interest, which are discussed below.
U.S. Pat. No. 3,890,166 (Kondis, hereinafter Kondis 1) relates to the milling of particulate aluminum in the presence of a material capable of sorbing onto the surface of the aluminum sufficiently to stabilize it and at the same time be readily displacable, thereby producing a reactive or pyrophoric aluminum (see Abstract). The whole of the patent is hereby incorporated by reference. Significantly, all of Kondis' actual working examples appear to relate to wet grinding, rather than dry grinding (for example see Table 1, "milling media"; Table 2, "milling conditions"; and Table 3, "carrier liquid".
U.S. Pat. No. 3,963,482 (Kondis hereinafter Kondis 2) is related to aforementioned Kondis 1. It teaches that "(i)mproved aluminum particulate suitable for powder metallurgy application is produced by wet-milling particulate aluminum in an inert atmosphere in the presence of a predetermined amount of oxygen to thereby comminute the aluminum into finer particles while oxidizing the new surfaces of such particles and then, after the supply of oxygen is exhausted, welding together such particles by further milling to provide a larger aluminum particle having aluminum oxide dispersed therein (see Abstract). The whole of this patent is also hereby incorporated by reference.
There is also extensive trade literature concerning aluminum powders that are commercially available. "Alcoa Aluminum Powder in the Chemicals and Plastics Industries" is of particular interest since the aluminum used in the examples of the invention hereinafter was obtained from Alcoa and aforementioned Kondis assigned his patents to Alcoa. FIGS. 7 and 8 of the reference relate to the production of linear primary alcohols from activated aluminum powder, wherein aluminum alkoxides are intermediates.
Applicants' copending application Ser. No. 656,380, filed Oct. 1, 1984, includes a conventional method of preparing di-isobutyl, n-butyl aluminum alkoxide (see it's Comparative Example C-1). In that example, no dry-grinding was performed.
In sum, even with the benefit of hindsight, none of the aforementioned references disclose or suggest the invention claimed hereinafter which is restricted to dry grinding.